1. Field of the Invention
This invention relates to a filmless dental radiography system, and more particularly to a filmless dental radiography system that includes an intra-oral radiation sensor that operates in a manner that efficiently uses and effectively conserves electrical power.
2. Description of the Related Art
Dentists and oral surgeons typically use x radiation to obtain images of their patient's teeth, mouths and gums to aid in diagnosis and treatment. In traditional oral and dental radiography, a cartridge containing photographic film is placed in the patient's mouth, for example behind a patient's tooth, and an x-ray beam is projected through the tooth and onto the film. The film, after being exposed in this manner, is developed in a dark room or a closed processor using special chemicals to obtain a photographic image of the tooth.
More recently, the field of filmless dental radiography has emerged. In filmless dental radiography, an x-ray beam is still projected through the patient's tooth, but no photographic film is used. Instead, an electronic sensor is placed in the patient's mouth behind the tooth to be examined. The electronic sensor may include a charge-coupled device (CCD), a complementary metal-oxide semiconductor (CMOS) active pixel sensor (APS) array or any other filmless radiation sensor. The x-rays pass through the tooth and impinge on the electronic sensor, which converts the x-rays into an electrical signal. The electrical signal is transmitted to a computer, either directly or through a module containing intermediate processing circuitry. The computer then processes the signal to produce an image on an associated output device, such as a monitor or a printer.
Filmless dental radiography offers several advantages over traditional film-based radiography. Most importantly, the electronic sensor is much more sensitive to x-rays than is film, allowing the dosage of x-rays to the patient to be lowered by as much as 90%. Also, the image of the tooth is generated by the computer almost instantaneously, thus eliminating the entire development process, including the use of potentially harmful chemicals. In addition, because the images are generated electronically, they can be stored electronically in a computer database.
Examples of filmless dental radiography systems include those described in U.S. Pat. No. 4,160,997 to Robert Schwartz and U.S. Pat. No. 5,434,418 to David Schick.
One of the issues with a filmless dental radiography is that an electronic sensor, unlike a piece of photographic film, must be provided with electrical power in order to be operational. This means that some component or components for generating and delivering the power must be utilized. In some conventional systems, electrical power is provided via a cable that connects the sensor to a processing system. For example, in U.S. Pat. No. 6,134,298 to David Schick et al., a system is described in which an electronic sensor 1 receives power via a cable from a remote board 2, which remote board 2 itself includes a power supply 30 that couples with the V and GND lines of a Universal Serial Bus (USB) connected to a personal computer. Thus, in the system of the '298 patent, electrical power to the sensor is provided from the computer, which itself may be provided by a relatively large battery internal to the computer, or an AC supply of power. The amount of power available, therefore, is relatively abundant, and operating the sensor in a manner that efficiently uses an effectively conserves power is less of a concern.
In other configurations, however, an electronic sensor may not have available to it such an abundant supply of electrical power, and in those situations power conservation is a paramount concern. For example, in a filmless dental system in which there is no cable or wire between the electronic sensor and the image processing system, electrical power to the various components of the sensor is provided typically by a power source, such as for example by a battery, integrated into the sensor itself. Due to the constraints on the size of the sensor, which must be small enough to fit comfortably into a patient's mouth, the on-sensor power source must be quite small, and therefore quite limited in the amount of power it can provide.
U.S. Patent Application Publication No. US 2001/0055368 A1 to Carroll describes a sensor which it contends communicates via a wireless link, and which it contends includes a rechargeable battery for powering the sensor. However, there is nothing in the 2001/0055368 application which discusses the important topic of power conservation, or describes how to configure and operate the sensor such that it can function effectively using only the limited amount of electrical power that such a rechargeable battery would provide.
There is a need, therefore, for a filmless dental radiation system that takes an entirely fresh approach, and includes a sensor designed to operate in a manner that efficiently uses and effectively conserves electrical power, and which thereby can function for its intended purposes even in situations in which the amount of electrical power available is limited.